Mongoid：has_and_belongs_to_many幽會不會觸發after_save的

Question

我有下面的代碼：

def Person 
    has_and_belongs_to_many :houses 

    def after_save do 
    p "After save" 
    end 
end 

def House 
    has_and_belongs_to_many :persons 
end 

p = Person.create 
h = House.create 
p.house_ids 
=> nil 

p.houses << h # it should print 'After save' 
p.house_ids 
=> ["540591aad9a0d13cee00003e"] 

它應打印「保存後」，但它不會觸發回調，爲什麼不呢？

Answer 1

因爲after_save不會被觸發創建對象時，...利用after_create回調，它會正確打印